Testing by the Insurance Institute for Highway Safety found flaws with the safety systems of self-driving cars and issued a warning saying the issues could put passengers at risk, The Hill reports.

In a paper, titled "Reality Check," the IIHS issued a warning cars and trucks with electronic driver assist systems repeatedly either failed to see stopped vehicles, did not stop in time when obstacles were in the way and even steered drivers into a crash if they were not paying attention.

The organization tested the Tesla Model S, Tesla Model 3, BMW 5 Series, Mercedes-Benz E-Class, and Volvo S90 on the safety of their adaptive cruise control and active lane-keeping performance.

"We have found situations where the vehicles under semi-automated control may do things that can put you and your passengers at risk, and so you really need to be on top of it to prevent that from happening," said David Zuby, the institute's chief research officer.

The IHHS set all cars to 31 miles per hour and pointed them at a stationary target. BMW, Volvo and Mercedes self-driving cars' lane-centering system failed during tests, especially on curves or hills. The vehicles, "steered toward or across the lane line regularly," requiring driver intervention, the IIHS said.

All of the vehicles except the Tesla's Model 3 failed to respond to stopped vehicles ahead of them. Tesla's Model S and Model 3, though, failed to stop in time during tests on track with the company's adaptive cruise control turned off. When the cruise control was turned in the Tesla, the vehicle stopped before hitting the target.